Wheels for automotive vehicles are typically made of suitably strong and durable metal alloys. They usually comprise a hub for attachment to a vehicle axle and/or braking mechanism, and a rim for carrying a specified vehicle tire, typically a pneumatic tire. The hub and rim are often connected by a suitable number of radial spokes. The wheel has an inner side facing the vehicle structure to which it is attached, and an outer side visible to a viewer. In addition to its structural function, the visible side of the wheel may be designed for an intended visual effect for enjoyment by the owner or other viewer.
Both for appearance and to maximize air flow to the brakes, automobile wheel styling has tended to emphasize open designs in which the tire-bearing rim is supported on slender spokes or columns connecting the rim to the hub. This design is particularly prevalent for lighter weight alloy (aluminum or magnesium) wheels and conveys the additional benefit of further reducing wheel mass.
The number and cross-section of the spokes is dictated by both structural and aesthetic considerations, leading to a wide range of wheel and spoke designs. In some wheels the spokes are solid with a cross-section which may be generally rectangular, triangular, trapezoidal or oval. Such solid spokes may be of uniform or variable section along their length and in some designs a single spoke at the hub may be split into two spokes of smaller cross-section at the rim. In other wheels the spoke, at least in part, has the form of a channel section, which, in cross-section, may resemble a “C” or a “U”. Some wheels may employ only a single spoke design, but wheels employing more than one spoke design, alternating in regular pattern around the wheel may also be found.
Irrespective of the spoke design or configuration, in vehicle use, these spokes will repeatedly flex under the bending loads applied during cornering maneuvers. Such deflections can affect wheel lateral stiffness which could result in poorer ride comfort. Considerable attention is therefore directed to ensuring that the spokes are suitably stiff under bending loads to limit flexure to acceptable levels. But since the spoke stiffness, for a given material, will be determined by the spoke section, increasing spoke stiffness often results in a higher than preferred mass.
There is therefore interest in alternative approaches to achieving low mass spoked wheel designs with acceptable spoke stiffness.